Yes, there should be a rubber mounding/gasket along the top of the skirt.
I’m not sure if I’m following the rest of your question. If you’re asking how the fender skirts should be installed, then:
When I first got my ‘57, I could not for the life of me get the fender skirts back on after the first time I took them off. I read every description that I could possibly find for how to do it and tried many times, but I just couldn’t do it. However: I eventually found this video, which somehow clicked something in my brain:
. (The video is for a 55 rather than a 57, but the process was exactly the same on my 57). Your mileage may vary, of course: I’m not particularly mechanically inclined, so reading how to do it didn’t help me at all - I had to see it being done. Now I can get them off and on in literally two minutes. (Not a terribly useful life skill in the grand scheme, but gratifying to me nonetheless!)
If, on the other hand, you’re asking whether your fender skirts themselves have been assembled correctly - whether all the bits and pieces are in the right place and installed properly - I’m not enough of an expert to comment definitively. As I recall, though, the rear/backsides of my skirts don’t look like the pictures you posted. But I’ll go take a picture of mine tonight to confirm.